We have developed a method for making functional apical plasma membrane vesicles from cultured toad kidney cells. Sodium uptake was measured and was found to be inhibitable by amiloride with a K 05 about 10-7 M, in good agreement with the K 05 of 5 x 10-7 M previously measured in intact kidney cells. These vesicles were incorporated into planar bilayer membranes and amiloride-sensitive sigle Na channel activity was successfully recorded.